Marine engine exhaust system



United States Patent Inventors Appl. No.

Filed Patented Assignee MARINE ENGINE EXHAUST SYSTEM 20 Claims, 5 Drawing Figs.

US. Cl

Int. Cl

115/34, ll5/l7 B63h 21/26,

[50] Field ofSearch ll5/34, l7, 12, l2(A), 16

[56] References Cited UNITED STATES PATENTS 3,083,529 4/1963 Hamilton l 15/16X 3,249,083 5/1966 lrgens ll5/l2(A)UX Primary Examiner-Trygve M. Blix Attorney Wheeler, Wheeler, House and Clemency ABSTRACT: Disclosed herein is a marine propulsion device including a lower unit having an engine exhaust passageway and a propeller having a hub terminating in a generally cylindrical portion. The lower unit also includes means including a tin and an exhaust outlet located adjacent to the bottom of the fin or behind the fin for delivering exhaust gases from the passageway in the lower unit to the low pressure area behind the propeller hub created by propeller rotation. The fin can also include a concavely shaped surface located in relation to the propeller for directing water rotated by the propeller in the direction toward the propeller axis.

Patented- Nov. 3, 1970 I 3,537,419

I Sheet 1 of? F/G. 2 'NVENTORS 77/500025 J/fauzzwuu finale/vim Patented Nov. 3, 1970 3,537,419

Sheet 2 or 2 W, @M Mm fl/famw MARINE ENGINE EXHAUST SYSTEM BACKGROUND OF THE INVENTION This invention relates to marine propulsion arrangements and devices and, more particularly, to thrust increasing arrangements for marine propulsion devices. In the past, several arrangements have beenprovided for discharging exhaust gases from a marine propulsion unit through a propeller hub and into the void or vortex created by operation of the l propeller, thereby to reduce the drag associated with such vortexes. Examples of such constructions are found in the Kiekhaefer US. Pat. Nos. 3,246,698; 3,279,415, and 3,l02,506 and the Alexander US. Pat. Nos. 2,948,252 and 3,092,185.

SUMMARY OF THE INVENTION Effective delivery of the exhaust gases to the vortex without causing propeller blade ventilation or cavitation is provided by employment ofa propeller having a hub with a generally cylindrical terminal or rearward portion which may include a terminal flare and by employment of a fin which extends downwardly from the lower unit and rearwardly of the propeller to adjacent to or into the void or vortex caused by propeller operation, together with means for discharging exhaust gas relative to the fin so as to effect delivery of the exhaust gases into the propeller hub vortex.

In one embodiment of the invention, the fin is hollow and is provided adjacent the lower end thereof, with a discharge opening through which the exhaust gas is delivered to the propeller hub vortex.

In another embodiment of the invention, the fin is not hollow but is provided with a rear wall transverse to the direction of intended movement, behind which rear wallexhaust gas is discharged. During travel through the water, the fin creates a void or low pressure condition or cavity immediately behind the rear wall and when exhaust gases are delivered immediately rearwardly of this wall and into the low-pressure cavity, such gases will travel downwardly through the low-pressure cavity or void created by the fin and into the void or vortex created by the propeller hub.

One important object of the invention is to provide a marine propulsion device including means other than the propeller hub exhaust gas discharge arrangements for delivering exhaust gases into the central vortex or void created by propeller operation and without causing cavitation or ventilation of the propeller blades so as to thereby reduce the drag which otherwise results from a relatively low-pressure condition at the vortex of the propeller wake.

Another important object of the invention is to provide a marine propulsion device which includes a duct extending rearwardly of a propeller having a cylindrical terminal portion and adjacent to and into the central vortex or void created by operation of the propeller to afford introduction into the vortex of a gas such as air or engine exhaust gases. Such an arrangement increases thrust by decreasing the drag otherwise resulting from the lower pressure condition in the vortex in the propeller wake.

Still another important object of the invention is to provide a marine propulsion device including a fin, or the like. which extends rearwardly of a propeller having a generally cylindrical terminal portion and adjacent to or into the central vortex or void created by propeller operation, together with means for discharging exhaust gases behind the fin for travel downwardly and rearwardly of the fin into the vortex behind the propeller.

Another object of the invention is to provide a marine propulsion device having means for directing water rotated by the propeller in a direction affording thrust to the marine propulsion device while also affording ventilating of the lowpressure area behind the propeller hub created by rotation of the propeller, thereby decreasing the drag on the marine propulsion device and increasing the available thrust.

Another object of the present invention is to provide a marine propulsion device having means for counteracting any torque reaction which tends to effect steering of the marine propulsion device.

Other objects, features and advantages will become apparent from the following description and accompanying drawings in which:

FIG. 1 is a fragmentary elevational view of one embodiment of a lower unit of a marine propulsion device incorporating various of the features of the invention;

FIG. 2 is a view of the underside of the marine propulsion device shown in FIG. I;

FIG. 3 is an elevational view of another embodiment of a marine propulsion discharge arrangement in accordance with the invention;

FIG. 4 is a view of the underside of the marine propulsion I device shown in FIG. 3; and

FIG. 5 is a fragmentary view, partially in section, of a modified propeller which can be employed with the invention.

The invention is applicable to marine propulsion arrangements including the so-called inboard arrangements and to outboard motors and stern drive units. Such propulsion arrangements includes means for rotatably supporting a propeller which includes a hub and one or more extending blades and which is operatively connected to an engine. In this regard, there is fragmentarily shown in the drawings a marine propulsion device 10 which can be either a stern drive unit or an outboard motor and which includes a propulsion or lower unit 12 rotatably supporting a propeller 14. As compared to so-called jet drive outboard motors, the propeller 14 operates, under normal conditions, in a free stream of water and not within a tube or duct. The propeller 14 includes a sin- 'gle series of blades 15 and a hub 16 terminating at its rear in a generally cylindrical portion 17. The propeller I4 is generally rotatably about an axis 18. The propeller 14 is connected to an engine (not shown) by any suitable transmission means located in a gear case 19. An exhaust passageway 20 is carried on the lower unit 12 in communication with the engine (not shown).

Means are provided for delivering gas to the low-pressure area behind or rearward of the propeller hub 16, which lowpressure area is created by rotation of the propeller 14 and is commonly referred to as the hub vortex, and for directing the water flow rearwardly from the propeller so as also to increase the effective thrust. Any available gas source can be employed. For instance air at atmospheric pressure could be aspirated into the vortex due to the lower pressure condition existing in' the vortex. In the preferred embodiment, the exhaust gas of the engine is employed and the gas delivery means comprises a member or hollow duct or fin 22 communicating with the exhaust passageway 20 and having a discharge opening 24 disposed directly behind the propeller l4 and proximate the hub axis 18. As shown in FIG. 1 the exhaust passageway 20 excludes the hub 16 and therefore the hub is constructed without an axially extending exhaust gas passageway. The fin 22 is solely supported at its upper ends by connection to a cavitation plate 26 and extends downwardly, traversing the free water stream from a suitable aperture or opening25 in the cavitation plate 26. The termination of the fin is such that discharge opening 24 is generally disposed slightly above the center line 18 of the propeller. If desired, the fin 22 can be an integral part of the exhaust passageway.

In operation, exhaust gases discharged from the engine are delivered to the low-pressure area or hub vortex created by the rotation of the propeller 14 to thereby ventilate the hub vortex and decrease drag on the marine propulsion device 10.

case 119 supports a propeller shaft 1 114 which. under normal boat-driving operating conditions.

The reduction in drag is ultimately realized in increased thrust delivered by the marine propulsion device. Delivering the exhaust gases into the vortex of the propeller slip stream also serves to obtain quieter operation.

The fin 22 also serves to direct water rotated by the propeller in a direction affording additional effective thrust to the marine propulsion device 10. In the preferred embodiment, this feature is achieved by forming the member or fin 22 with a transverse cross-sectional configuration of airfoil shape. When viewed in a plane perpendicular to the fin 22 and parallel to the hub axis 18, the member 22 is angularly related to the axis 18 of the propeller so as to direct water rotated by the propeller in a direction parallel to the hub axis 18, thereby affording additional effective thrust to the marine propulsion device 10. The member 22 includes surfaces 30 and 32 which can be either flat. curved, or a combination thereof and which serve to deflect or direct the rotating water in a direction toward the direction of the axis 18 of the propeller l4 and preferably in a direction parallel to the axis 18 of the propeller 14. For example, the member 22 can be, in transverse section, of airfoil cross-sectional configuration to thereby decrease drag as the fin 22 travels through the water.

When incorporated in certain types of stern drive units which experience a torque reaction force affecting steering. the fin 22 can also serve as a means for counteracting such torque reaction forces. The water rotated by the propeller is redirected by the surface of the fin 22 to thereby create a resulting force tending to rotate the propulsion unit 10 about the steering axis 40. When the propulsion unit is traveling in a forward drive condition, the flow of water past the fin 22 counteracts the normal torque reaction force. thereby alleviating the effect of the torque reaction force on steering.

The embodiment shown in H0. 3 of the invention also includes a lower unit 112 which can be part of an outboard motor or stem drive unit including an engine (not shown) which, during operation. produces exhaust gases. The lower unit 112 includes a drive shaft housing 140 and a gear case 119 connected to the bottom of the drive shaft housing 140. The drive shaft housing 140 provides an interior exhaust gas passageway 120 communicating with the engine. and the gear 13 carrying a propeller rotates in an otherwise free stream of water moving rearwardly relative to the gear case 119 and propeller 114. As in the embodiment ofFlGS. 1 and 2, the propeller 114 includes a hub 116 and a single series of blades 115 extending from the hub 116. When mounted on the propeller shaft 113. the hub 116 is generally of solid construction, i.e.. the hub 116 does not include an axially extending exhaust gas passage or duct as is the case with propeller constructions offering the so-called through-the-hub exhaust. The hub 116 also terminates in a generally cylindrical portion 117 which, if desired. can include a rearwardly located. radially outwardly projecting flare 121 as shown in H6. 5.

in accordance with the invention, means are provided for delivering exhaust gas from the lower unit passagcway 120 into the low-pressure area behind the propeller 114. In the FIG. 3 embodiment, this means includes a fin 122 which is supported solely at its upper end from the lower unit cavitation plate 126, which. during normal boat-driving operation. traverses the free stream of water flowing past the propeller. and which is spaced rearwardly of the hub. Preferably, the fin 122 extends to adjacent to or inwardly of the vortex created by propeller operation. in addition. at the front end thereof, the fin 122 includes a lip or transverse section 142 which includes a rear wall 144 transverse to the direction of intended travel.

In contrast to the previously described embodiment wherein the fin 22 was hollow and the exhaust gas traveled through the fin 22 and was discharged through an outlet 24 adjacent to the communicating with the lower unit exhaust gas passageway 120 so as to provide for exhaust gas travel downwardly to the void or vortex created by the propeller operation. Such downward travel occurs through a void created adjacent to the rearward fin wall 144 by passage of the fin through the water. Thus, as shown in FIG. 3, the outlet is located in the cavitation plate of the lower unit at the upper end of the fin and immediately rearwardly of the rear wall 144 of the fin 122.

Of course, the outlet can also be located anywhere along the length of the fin so that a fin could be part hollow and part solid.

The fin 122 can be constructed to direct water rotated by the propeller in a directionaffording additional effective thrust as already generally disclosed. in addition. as also generally mentioned. any gas can be delivered to the propeller hub vortex to reduce drag and the invention is not solely limited to exhaust gas from an engine.

Various of the features of the invention are set forth in the following claims.

We claim:

1. A marine propulsion device including a lower unit provided with a propeller operable in a free stream of water under normal operating conditions and including a hub without an axially extending exhaust gas passage, said hub terminating with a cylindrical portion, said propeller also including only a single series of blades which extend from said hub, said propeller being operatively connected to an engine, an exhaust passageway communicating with the engine, and a hollow fin supported solely at its upper end by said lower unit and communicating with said exhaust passageway. sa i d fin being disposed behind said propeller. traversing the free water stream. and terminating with a discharge opening located proximate said hub for affording delivery ofexhaust gas to the low-pressure area behind the hub created by rotation of the propeller.

2. A marine propulsion device in accordance with claim 1 wherein said fin has an airfoil-shaped cross section in a plane perpendicular to said fin and parallel to the hub axis.

3. A marine propulsion device in accordance with claim 2 wherein said fin includes a surface disposed relative to said propeller for directing water rotated by said propeller in a direction parallel to the direction of the propeller axis.

. A marine propulsion device in accordance with claim 3 wherein said surface is arcuate.

5. A marine propulsion device in accordance with claim 3 wherein said surface is disposed in angular relation to the propeller axis.

6. A marine propulsion device including a lower unit provided with a propeller operatively connected to an engine. said propeller being operable in a free stream of water under normal operating conditions and including a hub without an axially extending exhaust gas passage, said hub terminating with a cylindrical portion, an exhaust passageway communicating with the engine. a fin supported solely at its upper end by said lower unit and communicating with said exhaust passageway, said fin being disposed behind said propeller, traversing the free water stream, and terminating with a discharge opening located proximate said hub for affording delivery of the exhaust gas to the low-pressure area behind the I hub created by rotation of said propeller. said fin having a bottom of the tin 22, in the FIG. 3 embodiment, the fin 122 is generally solid and means are provided in the lower unit 112 defining an outlet 124 located rearwardly of the fin 122 and cross-sectional configuration of airfoil shape. and a side surface disposed relative to said propeller for directing water rotated by said propeller in a direction toward the direction of the propeller axis, said surface having an arcuate shape and being generally angularly related to the propeller axis in a plane perpendicular to said fin.

7. A marine propulsion arrangement including a rotatably supported propeller operatively connected to an engine, said propeller being operable in a free stream of water under normal operating conditions and having a hub without an axially extending exhaust gas passage. said hub terminating in a cylindrical portion and only a single series of blades extending from said hub, and a gas duct supported solely at the upper end thereof by said lower unit and traversing said free water stream in spaced relation rearwardly from said hub for delivering gas from a gas passageway to the low-pressure area behind the propeller created by rotation of the. propeller.

8. A marine propulsion device including a lower unit having a rotatably carried propeller operatively connected to an engine, said propeller being operable in a free stream of water under normal operating conditions and including a hub without an axially extending exhaust gas passage, said hub terminating with a cylindrical portion, said propeller also including only a single series of blades which extend from said hub, an exhaust passageway communicating with the engine, and means supported solely at the upper end thereof by said lower unit, traversing the free water stream, and spaced from said hub for delivering exhaust gas from said passageway to the low-pressure area behind said propeller created by rotation of said propeller.

9. A marine propulsion device in accordance with claim 8 wherein said means for delivering exhaust gas from said passageway includes a hollow fin with an exhaust gas outlet therein.

10. A marine propulsion device in accordance with claim 8 wherein said means for delivering exhaust gas from said passageway includes a hollow fin with an exhaust gas outlet at the lower end thereof.

11. A marine propulsion unit in accordance with claim 8 wherein said means for delivering said exhaust from said exhaust passageway includes a fin supported solely at the upper end thereof by said lower unit, traversing the free water stream, and spaced from said hub and an exhaust gas outlet communicating with said exhaust gas passageway and located adjacent to the top of said fin and immediately rearwardly thereof.

12, A marine propulsion device including'a lower unit provided with a propeller operatively connected to an engine and having an axis about which said propeller is rotatable, said propeller being operable in a free stream of water under normal operating conditions,-and including a hub without an axially extending exhaust gas passage, said hub being concentric with said axis and terminating with a cylindrical portion, said propeller also including only-a single series of blades which extend from said hub, an exhaust passageway communicating with the engine, and a member communicating with said exhaust passageway and having a discharge opening disposed rearwardly of said propeller and generally proximate to said propeller, said member being supported solely at its upper end by said lower unit and traversing the free water stream.

13. A marine propulsion device including a lower unit having a rotatably carried propeller operable in a free stream of water under normal operating conditions and including a hub without an axially extending exhaust gas passage, said hub terminating with a cylindrical portion, said propeller also including only a single series of blades which extend from said hub, said lower unit further including a gas passageway, and means on said lower unit including a gas outlet communicating with said gas passageway and a fin supported solely at the upper end thereof by said lower unit, traversing the free water stream and spaced rearwardly from said hub for delivering gas from said passageway to the low-pressure area behind said propeller created by propeller rotation.

14. A marine propulsion device in accordance with claim 13 wherein said fin is hollow and said gas outlet is located in said fin.

15. A marine propulsion device in accordance with claim 13 wherein said gas outlet is located adjacent the top of said tin and immediately rearwardly thereof.

16. A marine propulsion device in accordance with claim 13 wherein said cylindrical portion has a radially outwardly extending rearward terminally located flare.

17. A marine propulsion device including a lower unit having a rotatably carried propeller operable in a free stream of water under normal operating conditions and including a hub without an axially extending exhaust gas passage, said hub terminating with a cylindrical portion, said propeller also including only a single series of blades which extend from said hub, said lower unit further including a gas passageway, and means for delivering gas from said passageway to the low-pressure area behind said propeller created by rotation of said propeller, said gas-delivery means including a fin supported solely at the upper end thereof by said lower unit, traversing the free water stream and spaced rearwardly from said hub, and a gas outlet in said lower unit located rearwardly of said fin and communicating with said gas passageway.

18. A marine propulsion device in accordance with claim 17 wherein said fin has a rearward wall transverse to the direction of intended travel.

19. A marine propulsion device including a lower unit having a rotatablycarried propeller operable in a free stream of water under normal operating conditions and including a hub without an axially extending exhaust gas passage, said hub terminating with a cylindrical portion, said propeller also including only a single series of blades which extend from said hub, said lower unit further including a gas passageway, a fin supported solely at the upper end thereof by said lower unit, traversing the free water stream and spaced rearwardly from said huh, and an exhaust gas outlet means located rearwardly of said fin and communicating with said passage for delivering gases rearwardly of said fin for travel downwardly and rearwardly of said fin to the low-pressure area behind said propeller created by rotation of said propeller.

20. A marine propulsion device in accordance with claim 19 wherein said fin has a rearward wall transverse to the direction of intended travel. 

